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mmc: block: Add new ioctl to send multi commands

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Certain eMMC devices allow vendor specific device information to be read
via a sequence of vendor commands. These vendor commands must be issued
in sequence and an atomic fashion. One way to support this would be to
add an ioctl function for sending a sequence of commands to the device
atomically as proposed here. These multi commands are simple array of
the existing mmc_ioc_cmd structure.

The structure passed via the ioctl uses a __u64 type to specify the number
of commands (so that the structure is aligned on a 64-bit boundary) and a
zero length array as a header for list of commands to be issued. The
maximum number of commands that can be sent is determined by
MMC_IOC_MAX_CMDS (which defaults to 255 and should be more than
sufficient).

This based upon work by Seshagiri Holi <sholi@nvidia.com>.

Signed-off-by: Seshagiri Holi <sholi@nvidia.com>
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Jon Hunter 2015-09-22 10:27:53 +01:00 • committed by Ulf Hansson
parent aaa58d0e93
commit a5f5774c55
2 changed files with 169 additions and 56 deletions
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19
include/uapi/linux/mmc/ioctl.h
View file

@ -45,8 +45,24 @@ struct mmc_ioc_cmd {
};
#define mmc_ioc_cmd_set_data(ic, ptr) ic.data_ptr = (__u64)(unsigned long) ptr
#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
/**
* struct mmc_ioc_multi_cmd - multi command information
* @num_of_cmds: Number of commands to send. Must be equal to or less than
* MMC_IOC_MAX_CMDS.
* @cmds: Array of commands with length equal to 'num_of_cmds'
*/
struct mmc_ioc_multi_cmd {
__u64 num_of_cmds;
struct mmc_ioc_cmd cmds[0];
};
#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
/*
* MMC_IOC_MULTI_CMD: Used to send an array of MMC commands described by
* the structure mmc_ioc_multi_cmd. The MMC driver will issue all
* commands in array in sequence to card.
*/
#define MMC_IOC_MULTI_CMD _IOWR(MMC_BLOCK_MAJOR, 1, struct mmc_ioc_multi_cmd)
/*
* Since this ioctl is only meant to enhance (and not replace) normal access
* to the mmc bus device, an upper data transfer limit of MMC_IOC_MAX_BYTES
@ -54,4 +70,5 @@ struct mmc_ioc_cmd {
* block device operations.
*/
#define MMC_IOC_MAX_BYTES (512L * 256)
#define MMC_IOC_MAX_CMDS 255
#endif /* LINUX_MMC_IOCTL_H */